This invention relates generally to earth moving and excavation equipment, and more particularly to equipment provided to finish grade sidewalk base material including crushed rock, in preparation for a concrete or asphalt sidewalk overlay.
Construction equipment provided to grade a road base or sidewalk base are well known, and have been employed in such work for quite some time. Typically, a sidewalk base, for a specified sidewalk site is prepared by grading the same to a specific elevation. This is sometimes followed by base material being brought in by truck or loader equipment which requires additional grading.
For this purpose, blade type grading equipment is usually employed along with a crew of construction workers using rakes, shovels and the like to add or take away material as needed by the operator of the finish grader. Accordingly, this process consumes a large amount of manpower, and is slow thereby tying-up resources that could be used else where on the construction site.
For example, one early sidewalk grader is disclosed in U.S. Pat. No. 2,664,794 issued in 1954 showing a hopper-like storage bin for spreading base material over a sidewalk area, as the storage bin is pulled or dragged along the sidewalk base area. This design requires constant loading of the hopper, and would also require a smooth ground in front of the machinery which is dragged.
Another early design is U.S. Pat. No. 2,825,984 issued in 1958 which discloses a sidewalk fine grader for grading the earth between steel edge forms laid down on grade to provide side-forms for pouring concrete sidewalks. Like the '984 patent, this device travels directly over the sidewalk base and also requires a pair of spaced base rails installed to guide the machine.
In 1962 U.S. Pat. No. 3,059,355 issued disclosing a curb and sidewalk grading device that is pulled by a tractor or the like between form-rails similar to the '954 device. In addition, this invention uses an internal rotating auger-like member disposed horizontally to grade the base material. This design would be difficult to operate with base material that is larger than fine granular material.
A later design is U.S. Pat. No. 3,566,759 issued in 1971 showing a mounting arrangement for sidewalk building equipment where a motorized, wheeled vehicle employs sensors to sense reference points to follow a predetermined path. This design is complicated, and requires pre-installation of reference points.
Various other later designs, include U.S. Pat. No. 3,651,588 issued in 1972, U.S. Pat. No. 3,914,064 issued in 1975, and U.S. Pat. No. 4,113,402 issued in 1978. These designs are based on complicated machinery that is built integrally with the grading apparatus thereby increasing its initial cost.
More recent inventions include U.S. Pat. No. 6,109,825 issued in 2000, U.S. Pat. No. 6,168,348 issued in 2001, and U.S. Pat. No. 6,322,287 issued in 2001 which show machines designed for the placement of material, wherein each of the same vary in complexity and consistency of intended results. In particular, the '287 reference relies on the upper edge of a concrete form to provide a reference point to grade the sidewalk base as the machine moves over the same.
Importantly, none of the designs noted above are intended to employ a point of reference provided by existing, permanent portions of road structures to finish grade a sidewalk base. Further, none of the above designs are intended to be used with common construction equipment that is not required to be positioned over the sidewalk base while advancing forward to grade the same.
Accordingly a need remains for a simple design to precisely grade and prepare the base of a sidewalk with reference to existing, permanent portions of an existing road structure, while minimizing the manpower required, and while quickly advancing the sidewalk grading process, minimizing the number of passes over the sidewalk base to complete the grading process.